Novel detection schemes and high resolution separations in microcolumn liquid separations
Sammanfattning: Three micro detectors were developed and studied using micro-liquidchromatography (micro-LC). An evaporative light scattering detector (ELSD) nebulizer was developed for use with flow rates ranging from 0.5 to 10 µL/min. The parameters that affect analyte response were investigated and the most influential were capillary tip position and nebulization gas flow rate. One unique advantage of thismicro detector is that it can be operated at ambient conditions which allows for the analysis of semi-volatile compounds.A radio activity monitor (RAM) flow cell was developed for use at 3 µL/min and was designed for coupling to mass spectrometry (MS). The parameters that affect analyte response and band broadening were studied. Reducing the solid scintillant particle size to 9 µm and efficiently packing the solid cells allowed for direct coupling to MS without compromising the chromatographic separation.A nano-electrospray ionization (BSI) source for MS was developed and coupled to nano-LC and capillary electrophoresis (CE). This source incorporated a 50 µm i.d. stainless steel tip that was coupled to the separation capillary. At flow rates of 100 nL/min a stable electrospray was achieved.A multi-use separations system was developed for isocratic and gradient elution micro-LC, capillary electrochromatography (CEC), and pressure CEC (PEC). The details of the system and studies on peak area and retention time repeatability are reported. Comparisons are made between nano-LC and CEC. On average, column efficiency is 57% greater for CEC compared to nano-LC using the same nanocolumn.
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